Shulou(Shulou.com)06/01 Report--

This article mainly introduces the relevant knowledge of Spring MVC interceptor and exception handling mechanism, the content is detailed and easy to understand, the operation is simple and fast, and has a certain reference value. I believe you will gain something after reading this article on interceptor and exception handling mechanism of Spring MVC. Let's take a look.

1. SpringMVC interceptor 1.1.The function of interceptor

Spring MVC's interceptor is similar to the filter Filter in Servlet development and is used for pre-processing and post-processing of processors.

The interceptor is connected into a chain in a certain order, which is called the interceptor chain (Interceptor Chain). After visiting the intercepted party

Method or field, the interceptors in the interceptor chain are called in the order they were previously defined. Interceptor is also a concrete implementation of AOP idea.

1.2 the difference between interceptor and filter the scope of use of filter (Filter) interceptor (Interceptor) is part of the servlet specification, and any Java Web project can be used by Spring MVC framework itself. Only projects that use Spring MVC framework can use interception scope. After configuring / * in url-pattern, you can intercept all resources to be accessed after / * * is configured in, and all resources can also be intercepted. However, you can use tags to exclude resources that do not need to be intercepted. 1.3 Quick start for interceptors

Customizing the interceptor is simple, with the following three steps:

1. Create interceptor class to implement HandlerInterceptor interface

two。 Configure interceptor

3. Test the interception effect of the interceptor

Create interceptor class to implement HandlerInterceptor interface

Public class MyHandlerInterceptor implements HandlerInterceptor {public boolean preHandle (HttpServletRequest request,HttpServletResponse response,Object handler) {System.out.println ("preHandle running..."); return true;} public boolean postHandler (HttpServletRequest request,HttpServletResponse response,Object handler) {System.out.println ("postHandler running....");} public void afterCompletion (HttpServletRequest request,HttpServletResponse response,Object handler) {System.out.println ("aferCompletion running...");}}

Configure interceptor

Test the interception effect of the interceptor\

@ ResponseMapping ("/ test1") @ ResponseBodypublic ModelAndView quickMethod () throws Exception {System.out.println ("Target method execution"); ModelAndView modelAndView = new ModelAndView (); modelAndView.addObject ("name", "bestcollc"); modelAndView.setViewName ("index"); return modelAndView;} Test results: preHandle running.... Target method executes postHandle running... AfterCompletion running...1.4 multi-interceptor operation

As above, when writing a MyHandlerInterceptor2 operation, test the execution order

1.5 interceptor method description method name indicates that the preHandle () method will be called before the request is processed. The return value of this method is of Boolean Boolean type. When it returns false, the request ends, and subsequent Interceptor and Controller will not be executed. When the return value is true, the preHandle square method postHandle () of the next Interceptor will be called. This method is called after the current request has been processed, provided that the return value of the preHandle method is true, and it will be called before the view return rendering of the DispatcherServlet, so we can operate on the ModelAndView object after Controller processing in this method. This method will be called after the whole request is completed. That is, it is executed after the DispatcherServlet renders the corresponding view, and only if the return value of the preHandle method is true can it be called. 2. SpringMVC exception handling 2.1exception handling

There are two types of exceptions in the system: expected exception and run-time exception RuntimeException. The former obtains exception information by catching exception, while the latter reduces the occurrence of run-time exception mainly by means of specification code development and testing.

The Dao, Service and Controller of the system are all thrown up through throws Exception and finally handed over by the SpringMVC front-end controller.

Exception handling is performed by the exception handler, as shown below:

2.2 two ways of exception handling

Use the simple exception handler SimpleMappingExceptionResolver provided by Spring MVC

Implement Spring's exception handling interface HandlerExcepionResolver to customize your own exception handler

2.3simple exception handler SimpleMappingExceptinResolver

SpringMVC has defined the type converter, and when using it, you can map the exception to the view according to the project situation.

Default error view

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.